(1) Field of the Invention
This invention relates to a paper sizing composition for use in paper making. More particularly, the invention relates to a paper sizing composition which is employed in the range of neutral to alkali without using aluminum sulfate as fixing agent.
(2) Description of the Prior Art
In the paper manufacturing industry, sizing agents that are prepared from natural rosins or modified rosins, and especially, fortified rosin sizing agents that are prepared by saponifying maleic-modified rosins, are regarded as most preferable ones and they are widely used. These sizing agents are used together with aluminum sulfate and they are fixed to paper fibers under acidic conditions of pH 4.0 to 5.0. Owing to the acidic conditions in the use of these sizing agents, the following disadvantages are caused to occur. That is, paper making machinery suffers from corrosion, the strength and durability of obtained paper are lowered, and inexpensive alkaline fillers such as calcium carbonate cannot be used because the alkaline fillers are decomposed under the acidic condition. Therefore, it has been difficult to reduce much the production cost for paper making.
For this reason, neutral sizing agents which can be fixed to wood pulp without using aluminum sulfate, were looked for and some neutral sizing agents which give excellent sizing effect in the range of neutral to alkali have been proposed. For example, such a sizing agent is known that alkylketene dimer is dispersed in water in the presence of cationized starch. The sizing agent is, however, defective in that the cost is high and it takes much time to produce desired sizing effect.
Besides the above sizing agent, several neutral sizing agents of alkenyl succinic anhydride type have been proposed.
In British Pat. No. 2,015,612, there is proposed "substituted succinic anhydrides having substituent groups of butene oligomers having 16 to 40 carbon atoms". The compounds, however, are not satisfactory yet in sizing effect.
In U.S. Pat. No. 3,821,069 is disclosed a sizing agent which comprises the reaction product between maleic anhydride and internal olefins that are represented by the following general formula: EQU R.sub.x --CH.sub.2 --CH.dbd.CH--CH.sub.2 --R.sub.y
wherein R.sub.x and R.sub.y are, respectively, alkyl radicals containing 4 to 10 carbon atoms.
In Japanese Laid-Open Patent Publication No. 57-154,495 is proposed a reactive sizing agent which consists of "an alkenyl succinic anhydride mixture that is produced by adding maleic anhydride to a mixture of straight chain internal olefins which have 8 to 18 carbon atoms and double bonds of which are almost evenly distributed to every position except .alpha.-position. These sizing agents are high in reactivity with paper fiber, however, they do not produce sufficient sizing effect. In addition, they are liable to be hydrolyzed and they reduce its effect with the passage of time. Furthermore, when they are dispersed in water with a dispersing agent such as cationized starch, they sometimes become gel soon after the preparation. Even when the gel is diluted with water, homogeneous dispersion cannot be obtained, and if it is used as it stands, paper making machines are soiled as well as sufficient sizing effect cannot be attained, which facts will cause several troubles in paper making processes.
As described above, the known sizing agents are not satisfactory in view of sizing effect, dispersibility in water and/or stability of dispersion. Therefore, development of a more desirable neutral sizing agent is eagerly wanted.